1. Field of the Invention
The present invention relates to a substrate processing method, and in particular to a substrate processing method that carries out processing on a substrate in which a to-be-processed layer, an intermediate layer, and a mask layer are stacked in this order.
2. Description of the Related Art
There has been known a wafer for a semiconductor device in which an oxide film containing impurities such as a TEOS (tetra ethyl ortho silicate) film, a conductive film such as a TiN film, an antireflective film (BARC film), and a photoresist film formed through CVD processing or the like are stacked in this order on a silicon base material (see, for example, Japanese Laid-open Patent Publication (Kokai) No. 2006-190939). The photoresist film is formed to have a predetermined pattern by photolithography and acts as a mask when the antireflective film and the conductive film are etched.
In recent years, as semiconductor devices have become increasingly downsized, a circuit pattern on a surface of the above described wafer has been required to be more finely formed. To form a fine circuit pattern, in the process of manufacturing a semiconductor device, it is necessary to make the minimum size of a pattern in the photoresist film small and form an opening (a via-hole or a trench) of a small size in a to-be-etched film.
However, the minimum size of a pattern in the photoresist film is determined by the minimum size that can be developed using photolithography, but there is a limit to the minimum size that can be mass produced using photolithography due to variations in focal length and so on. For example, the minimum size that can be mass produced using photolithography is about 80 nm. On the other hand, the machining size that fills the need for downsizing a semiconductor device is about 30 nm.
As described above, the required size of a semiconductor device is glowing smaller, and it is thus desired that a technique to form an opening of a size that fills the need for downsizing a semiconductor device in a to-be-etched layer will be developed.